This work investigated the reasons for the increase of surface ozone concentrations in perspectives of emission changes and meteorological variations. It’s found that meteorological variation is the major driving force to the ozone increase in South China. The paper is informative and generally well organized. My major concern is the negative bias of TROPOMI data (~20% based on previous validations), especially over urban areas, and the effect to the results due to the bias.  

My detailed comments are listed below.

1. Line 126-127: not clear about what this means. Do you mean the difference between NOx, NOy, and NOz? Please specify this.
2. Line 166-167: is the optimization done day by day, or on a monthly basis?
3. Line 216-217: the anthropogenic VOC emissions in China has grown significantly from 2010-2017, driven by solvent use. I don’t think it can be ignored.
4. Line 221-222: can you elaborate more on the HCHO uncertainties?
5. Figure 2. For (c), it seems that the VOC emission changes are mainly from biogenic or open biomass burning for Southeast Asia, instead of anthropogenic sources.
6. Line 294: previous validations have found that TROPOMI NO₂ product has negative bias of ~20%, especially over urban areas (Verhoelst et al., 2021, Judd et al., 2020, Li et al., 2021). How will this bias affect the validation and your conclusions?

References:

Verhoelst, T., Compernolle, S., Pinardi, G., Lambert, J.-C., Eskes, H. J., Eichmann, K.-U., et al. (2021). Ground-based validation of the Copernicus Sentinel-5P TROPOMI NO2 measurements with the NDACC ZSL-DOAS, MAX-DOAS and Pandonia global networks. Atmospheric Measurement Techniques, 14(1), 481–510. https://doi.org/10.5194/amt-14-481-2021

Judd, L. M., Al-Saadi, J. A., Szykman, J. J., Valin, L. C., Janz, S. J., Kowalewski, M. G., et al. (2020). Evaluating Sentinel-5P TROPOMI tropospheric NO2 column densities with airborne and Pandora spectrometers near New York City and Long Island Sound. Atmospheric Measurement Techniques, 13(11), 6113–6140. https://doi.org/10.5194/amt-13-6113-2020

Li, M., McDonald, B. C., McKeen, S. A., Eskes, H., Levelt, P., Francoeur, C., Harkins, C., He, J., Barth, M., Henze, D. K., Bela, M. M., Trainer, M., de Gouw, J. A., and Frost, G. J.: Assessment of Updated Fuel-Based Emissions Inventories Over the Contiguous United States Using TROPOMI NO2 Retrievals, Journal of Geophysical Research: Atmospheres, 126, e2021JD035484, https://doi.org/10.1029/2021JD035484, 2021.